1. Field of the Invention
The present invention relates to controlling brightness in an image display device, and more particularly, to controlling brightness in a flat panel display, for example, such that each pixel of the display device has the same brightness for a given image signal.
2. Description of the Related Art
An image display device, such as a flat panel display, which generally includes groups of column electrodes and row electrodes arranged in a matrix, uses a driving circuit connected to each of the groups of electrodes to represent images. To improve the manufacturing efficiency and reduce the size of flat panel displays and their manufacturing costs, the driving circuit is typically connected to one side of the group of column electrodes or one side of the group of row electrodes. Accordingly, areas on the screen that are far from the driving circuit have poorer brightness characteristics than areas on the screen that are in close proximity to the driving circuit due to the resistance of the material of the electrodes of the flat panel display and the capacitance between the electrodes.
One method of representing a gray scale in a flat panel display controls the brightness with a driving circuit to drive a group of column electrodes in response to the amplitude of a voltage applied to the column electrodes by using amplitude modulation. The farther a column electrode is from the driving circuit, the smaller the voltage provided by the driving circuit. In order to prevent this phenomenon, a voltage V1 is applied to a first row electrode for a predetermined image signal and a voltage VN is applied to a last row electrode for the predetermined image signal, and the farther the row electrode is from the driving circuit, the larger the voltage provided to the row electrode by the driving circuit. Accordingly, the same voltage can be applied to each pixel placed along the group of column electrodes by compensating for voltage variations that depend on the distance between each row electrode and the driving circuit. Therefore, each pixel in a column can display uniform brightness.
However, in such a method of controlling brightness using amplitude modulation, the voltage applied to each column electrode must be varied in order to prevent brightness deteriorations in the columnar direction. Therefore, a power supply circuit and a control circuit are additionally required, which results in an increase in power consumption and cost.